Read the label on a tube of caulk and it’s likely to promise the world: "50 years," "lifetime durability," "guaranteed." Superlatives abound, exclamation points are in order. "Exceptional adhesion," "permanent flexibility," "all purpose." Flip the tube over and read the small print, however, and you’ll find that the warranty is practically worthless because it only covers replacement cost for the caulk itself. The stakes are a lot higher than that if you’re relying on caulk to seal out the weather on a new home or remodel. Faced with a shelf displaying ten different products, each claiming "superior performance" and "adheres to most surfaces," how do you choose? Researching this article was a chance to retest my old prejudices and preferences, and see how the new formulations compared with the products I used seven years ago when I was still in the trades. I went through almost 50 tubes of sample caulks on a variety of substrates. I concentrated mainly on the high-performance caulks — the ones designed for moving joints and that meet the ASTM C-920 standard (see ""). In the end, my own simple testing did far more to inform me than all of the hours spent talking to technical experts. I formed definite opinions that would influence my buying if I had to caulk a joint tomorrow.

Before you buy a tube of high-performance caulk, ask yourself why you’re buying it. Is the caulk your main line of defense for keeping out the weather, or do you have some backup protection underneath? Caulking is not a substitute for proper flashing and weatherproofing. For example, no amount of caulking will make a vinyl siding job waterproof...

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